/**
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 */
package com.aelitis.azureus.launcher.classloading;

import java.io.File;
import java.lang.ref.WeakReference;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;

/**
 * @author Aaron Grunthal
 * @create 28.12.2007
 */
public class PrimaryClassloader extends URLClassLoader implements PeeringClassloader {

    private final ArrayList peersLoaders = new ArrayList();
    private final ClassLoader packageLoader;

    private static final String packageName = PrimaryClassloader.class.getPackage().getName();

    /**
     * initialization path when loaded through bootstrapping
     */
    private PrimaryClassloader() {
        super(generateURLs(), getSystemClassLoader().getParent());
        this.packageLoader = getSystemClassLoader();
    }

    /**
     * initialization path when loaded via <code>-Djava.system.class.loader=com.aelitis.azureus.launcher.classloading.PrimaryClassloader</code>
     * instead of bootstrapping, has the advantage that this gets registered as system classloader
     * 
     * @deprecated DO NOT INVOKE MANUALLY
     */
    public PrimaryClassloader(ClassLoader parent) {
        super(generateURLs(), parent.getParent());
        this.packageLoader = parent;
    }

    private static URL[] generateURLs() {
        String classpath = System.getProperty("java.class.path");

        String[] paths = classpath.split(File.pathSeparator);
        URL[] urls = new URL[paths.length + 1];
        try {
            for (int i = 0; i < paths.length; i++) {
                urls[i] = new File(paths[i]).getCanonicalFile().toURI().toURL();
                System.out.print(urls[i] + " ; ");
            }

            urls[urls.length - 1] = new File(".").getCanonicalFile().toURI().toURL();
            System.out.println(urls[urls.length - 1]);
        } catch (Exception e) {
            System.err.println("Invalid classpath detected\n");
            e.printStackTrace();
            System.exit(1);
        }

        return urls;
    }

    /**
     * altered class lookup
     * <ol>
     * <li>follow normal delegation, circumventing the system classloader as we bootstraped it away</li>
     * <li>OR delegate to the system classloader iff it is for classes from this package, this allows us to rebootstrap and discard other branches in
     * the hierarchy</li>
     * <li>check for loaded by peers</li>
     * <li>try to load from peers</li>
     * </ol>
     */
    protected Class loadClass(final String name, boolean resolve) throws ClassNotFoundException {
        // System.out.println(this+" loading "+name);
        Class c;
        try {
            if (!name.startsWith(packageName))
                c = super.loadClass(name, resolve);
            else
                c = packageLoader.loadClass(name);
        } catch (ClassNotFoundException e) {
            c = peerFindLoadedClass(name);
            if (c == null)
                c = peerLoadClass(name);
            if (c == null)
                throw e;
            if (resolve)
                resolveClass(c);
        }
        return c;
    }

    private Class peerFindLoadedClass(String className) {
        Class c = null;
        synchronized (peersLoaders) {
            for (int i = 0; i < peersLoaders.size() && c == null; i++) {
                WeakReference ref = (WeakReference) peersLoaders.get(i);
                SecondaryClassLoader loader = (SecondaryClassLoader) ref.get();
                if (loader != null)
                    c = loader.findLoadedClassHelper(className);
                else
                    peersLoaders.remove(i--);
            }
        }
        return c;
    }

    private Class peerLoadClass(String className) {
        Class c = null;
        synchronized (peersLoaders) {
            for (int i = 0; i < peersLoaders.size() && c == null; i++) {
                WeakReference ref = (WeakReference) peersLoaders.get(i);
                SecondaryClassLoader loader = (SecondaryClassLoader) ref.get();
                if (loader != null) // no removal here, peerFindLoadedClass should take care of that anyway
                    c = loader.findClassHelper(className);
            }

        }
        return c;
    }

    void registerSecondaryClassloader(SecondaryClassLoader loader) {
        synchronized (peersLoaders) {
            peersLoaders.add(new WeakReference(loader));
        }

    }

    /**
     * 
     * @param toRun
     */
    public static ClassLoader getBootstrappedLoader() {
        ClassLoader loader = ClassLoader.getSystemClassLoader();

        try {
            return (ClassLoader) loader.loadClass(PrimaryClassloader.class.getName()).newInstance();
        } catch (Exception e) {
            System.err.println("Could not instantiate Classloader\n");
            e.printStackTrace();
            System.exit(1);
            return null;
        }
    }
}
